Dominant Hand May Begin in Womb

Are we born either right- or left-handed, or do we randomly choose a dominant hand as young children? The answer to this question has been debatable, as it takes a few months for a newborn to grasp an object, a few years to draw, and then to write, leading to the possible preference for the use of one hand or other parts of the body.

Now a new Italian study published in the journal Scientific Reports suggests that hand preference is already well-defined by the 18th week of gestation and that the motor system is highly sophisticated by this point.

By watching and analyzing the body movements of 29 fetuses — a branch of study known as fetal kinematics — the researchers were able to predict the motor preference of each child at age nine with an accuracy rate between 89 to 100 percent, depending on the parameters used.

The predictive capacity of this technique may also be a good starting point for the early detection of pathologies characterized by cerebral asymmetries, such as depression, schizophrenia, and autism spectrum disorders.

In particular, the researchers analyzed the hand movements of the fetuses at the 14th, 18th, and 22nd week of gestation using a 4D ultrasound scan, observing the three dimensional image in real time and in movement, in 20-minute sessions.

They analyzed three types of movements: two of greater precision, directed to the eyes and mouth, and one directed to the uterine wall, as a control. The findings show that starting from the 18th week the fetuses execute significantly more quickly the movements requiring precision with that which will become the preferred hand.

The study, led by Valentina Parma, Ph.D., researcher at the International School for Advanced Studies (SISSA of Trieste, Italy), and Professor Umberto Castiello of the University of Padua in Italy, shows the high level of maturation and specialization of the motor system in utero.

The findings have significant implications, reaching far beyond hand preference alone. In fact, the accuracy of fetal kinematics opens new perspectives for use in the clinical field.

For example, hand preference is due to the prevalence of one cerebral hemisphere over the other. The effect is contralateral, meaning that each hemisphere is responsible for the opposite side of the body.

This characteristic has sometimes been associated to pathologies which involve a cerebral asymmetry, such as depression, schizophrenia and autistic spectrum disorders. Research has shown that left-handed people are more likely to suffer from psychotic disorders, such as schizophrenia.

Fetal kinematics could be used to identify new markers that might allow doctors to intervene at an early stage and help mitigate development problems.

Source: Scuola Internazionale Superiore di Studi Avanzati